Coral
is pretty looking stuff at the bottom of the sea. But it's more
than that, as the curious growths of intricate patterned coral
formations are made of vast numbers of small animals forming a
living surface over hard stuff which they have generated, made of
chalk. Like trees in a forest, the underwater branches of coral
harbour myriad creatures in a diverse ecosystem.

"Coral
reefs occupy half a percent of the sea floor, yet they support a
quarter of all marine species" - a quote from LIFE, BBC1

It
would be good to preserve this, partly because we like
interestingness in nature and biodiversity which continues to
survive, but also because coral reefs take away carbon dioxide and turn
it into solid calcium carbonate limestone. Each square metre of
coral can produce ten grammes of calcium carbonate per day,
representing 2.4 litres of CO2 gas removed from the atmosphere.
That's carbon sequestration that
actually works! Coral reefs are also good for the tourist
industry, and for making restful documentaries about marine life.
The life on a coral reef makes a good job of turning unsightly
shipwrecks into interesting ornamental objects for visitors to
gaze at, and having all that stuff down there at the bottom of
the sea helps to reduce the ravages of natural disasters
attacking the coastline; tsunamis, hurricanes, etc.

Coral
has uses, (and I don't mean as tourist souvenirs!). As the
skeletal material has a honeycombed structure, it can be used as
surgical substrate to replace missing bone. The body tends to
accept it as natural and grows new bone where it was.